The present invention relates to CVD (chemical vapor deposition) chambers for depositing conductive and insulative material layers on semiconductor wafer substrates. More particularly, the present invention relates to a tool for preventing diffusion of toxic, corrosive and/or flammable process or cleaning gases from a CVD chamber during periodic chamber cleaning and maintenance.
Semiconductor processing is carried out in specialized apparatus including multiple chambers wherein semiconductor wafers are processed by the deposition of multiple conductive and insulative layers on the wafers and treatment of the layers to form integrated circuits on the wafers. A common process involved in manufacturing integrated circuits on semiconductor wafer substrates includes depositing a dielectric layer over a metal region on a substrate; etching multiple openings in the dielectric layer such that each opening exposes a contact area on the region; and then filling each opening with an electrically-conductive material using a chemical vapor deposition (CVD) process to form a plug that establishes electrical contact with the contact region. Tungsten is one of the metals most commonly used to form the electrically-conducting plug. However, formation of a tungsten plug using tungsten chemical vapor deposition processes requires the use of several toxic, corrosive, and pyrophoric process chemicals and gases. Table 1 lists some of the common hazardous gases used in a typical tungsten chemical vapor deposition processes, along with the chemical symbol/formula, health and fire hazards and hazardous concentrations of each.
Argon and nitrogen, while common, innocuous and nonflammable gases, must be handled with caution because these gases can cause asphyxiation by displacing oxygen necessary for breathing. Hydrogen, another relatively innocuous gas, is a flammable asphyxiant. SiH4 is toxic and reacts with atmospheric air to form corrosive silicic acid. WF6 is also toxic and reacts with atmospheric moisture to form hydrofluoric acid. To avoid leakage of these gases from the chamber during wafer substrate processing, a vacuum is continually maintained in the chamber by operation of a vacuum line connected to the chamber. The gases are thus drawn from the chamber interior through the vacuum line, where they are disposed of using conventional equipment and techniques.
In active semiconductor fabrication process chambers, particularly those in which etching or chemical vapor deposition processes are carried out, residues frequently form on the walls and other surfaces of the chambers during processing. Accordingly, regular periodic chamber cleanings between wafer processing cycles is necessary for maintaining CVD system performance in the production of high-quality integrated circuit devices. Such periodic chamber cleanings may be conducted without breaking the chamber vacuum seal. Preventative maintenance (PM) chamber cleanings, on the other hand, are performed between multiple periodic chamber cleanings and do require that the chamber vacuum seal be broken because the chamber lid must be opened in order to facilitate physically wiping down the chamber interior.
Table 2 lists two potentially hazardous gases, HC-116-hexafluoroethane and oxygen, which are commonly used in the periodic cleaning of CVD chambers, along with the chemical symbol/formula, health and fire hazards and hazardous concentrations of each.
Although the vacuum seal maintained in the chamber system during the periodic chamber cleanings facilitates removal of most of the process gases and cleaning gases from the chamber, small quantities of these gases typically remain in the chamber interior when the chamber lid is opened to commence PM chamber cleaning. Because these process gases and cleaning gases are potentially harmful to process engineers and other cleaning or maintenance personnel in the immediate vicinity of the processing chambers, great care must be taken by such personnel to avoid exposure to these residual gases during PM chamber cleanings. Moreover, hydrogen peroxide, commonly used in the wet cleaning of the chamber interior during PM chamber cleanings, breaks down into water and hydrogen, and the water reacts with chamber deposits to form the corrosive and toxic hydrogen fluoride (HF).
According to industrial sanitation and safety standards, if potential toxic substances exist in a workplace, the first priority of health and safety personnel should be to eliminate or control the root causes or sources of such substances. The next priority is to eliminate or reduce toxin transference from the source to the personnel. The last priority is the direct protection of personnel by the use of masks, respirators or other equipment. Because no such method of direct protection is suitable for all situations and is incapable of total protection, however, the most effective prevention methods involve eliminating or controlling the root causes or sources of the toxic substances. Accordingly, a device is needed for preventing escape of toxic and corrosive gases from a CVD chamber during periodic maintenance chamber cleanings.
An object of the present invention is to provide a preventative maintenance tool for preventing exposure of personnel to harmful gases emanating from a process chamber.
Another object of the present invention is to provide a preventative maintenance tool for containing corrosive and toxic gases in a chemical vapor deposition (CVD) chamber during maintenance of the chamber.
Still another object of the present invention is to provide a preventative maintenance tool which provides access to the interior of a CVD chamber while preventing escape of potentially corrosive, toxic and harmful gases and chemicals from the chamber interior.
Yet another object of the present invention is to provide a preventative maintenance tool which may be removably installed on a variety of CVD chambers.
A still further object of the present invention is to provide a preventative maintenance tool which is simple in construction and installation.
Yet another object of the present invention is to provide a preventative maintenance tool which is versatile and simple in operation and enables complete access to the interior of a CVD chamber for thorough cleaning thereof.
Still another object of the present invention is to provide a preventative maintenance tool which substantially eliminates the need for chamber cleaning and maintenance personnel to wear protective equipment during preventative maintenance cleaning of a CVD chamber.
In accordance with these and other objects and advantages, the present invention is a preventative maintenance tool which may be installed on a metal chemical vapor deposition (CVD) chamber to prevent escape of contaminating and toxic gases from the chamber interior during preventative maintenance (PM) cleaning of the chamber. The tool comprises a cylindrical tool body which fits to the lid O-ring of the chamber to form a gas-tight seal therewith; a vacuum line connector nipple extending from the body for connection to a vacuum line; and a lid panel rotatably mounted in the body and fitted with a pair of hinged closing panels for reversibly sealing the chamber and facilitating chamber cleaning.